Gloss Measurement: A Comprehensive Guide to Gloss Meter Technology

Gloss meter is an instrument used to measure the surface gloss of ceramics, paints, inks, plastics, marble, aluminum, electroplating, hardware and other materials.
Gloss is an important optical index for the appearance of an object, reflecting the specular reflection ability of the material surface, and GU is usually used as the unit of gloss.

Gloss is a physical quantity that evaluates the ability of a material surface to reflect light under a set of geometrically specified conditions. Therefore, it expresses reflective properties with direction selection. According to the characteristics of the gloss, the gloss can be divided into several categories. The gloss we usually refer to is “specular gloss”, so the gloss meter is sometimes called the specular gloss meter. Gloss is completely different from the concept of “smoothness” or “roughness” in the machining industry, which is the evaluation of the slight unevenness of the surface of the material.

The principle of gloss meter:
1: Gloss is a physical quantity that evaluates the ability of the surface of a material to reflect light under a set of geometrically specified conditions, and it has a direction-selective reflection property. The gloss we usually refer to refers to “specular gloss”, so the gloss meter is sometimes called “specular gloss meter”. Gloss is completely different from the concept of “smoothness” or “roughness” in the machining industry, which is a continuation of the slight unevenness of the surface of the material.

2: The measurement principle of the gloss meter is shown in the figure “Measurement Principle”. The measuring head of the instrument is composed of a transmitter and a receiver. The transmitter is composed of an incandescent light source and a set of lenses, which generate a certain required incident beam. The receiver consists of a lens and a photosensitive element for receiving the cone beam reflected from the sample surface.
Specular Gloss is a relative measure of specular gloss. The reference standard is black glass with a refractive index np=1.567. Assuming that the plane is in an ideally polished state, the natural beam is mirror-reflected by the plane, and the gloss value at this time is defined as 100.0 gloss units.

According to the gloss value, the gloss board is divided into three types: high, medium and low. High gloss panels are made of black optical glass or other materials. Medium-gloss and low-gloss panels are available in glazed ceramic or black optical glass frosted. The gloss meter uses the principle of light reflection to measure the gloss of the sample. That is: the sample is irradiated under the conditions of a specified incident angle and a specified beam, and the reflected light in the direction of the specular reflection angle is obtained.

Many optical properties of materials can be explained qualitatively by wave theory. According to the wave theory, the ratio of the energy W of incident light passing through a unit area per unit time to the energy flow W of reflected light can be derived.

W1 sin2(i-r) tg2(i-r)
——=[——————— + ——————]
W02 sin2(I+r) tg2(i-r)
In the formula, i is the angle between the incident light and the normal (incident angle),
r is the angle of refraction.

Gloss is the property of directional selective reflection on the surface of an object. Different bright spots appear on the surface or images of objects superimposed on the surface are formed. Gloss is the reflection ability of the surface of an object when it is irradiated by light. It is usually expressed by multiplying the reflectance of the sample in the mirror (regular reflection) direction relative to the standard surface by 100, that is, G=100R/R.

R in the formula—reflectivity of the sample surface, /R. – the reflectivity of the standard plate. Taking the polished black glass as a reference standard plate, the refractive index of sodium D rays is 1.568, and the specular gloss for each geometrical optical condition is calibrated to 105 gloss units.

How to use the gloss meter?
(1) switch machine
Press and hold the “Switch/Measurement Button” for 3 seconds to turn it on, the indicator light will light up and display the Logo interface. After a few seconds, the instrument will automatically enter the measurement interface. After turning it on, press and hold the “Switch/Measurement Button” for 3 seconds to turn it off. If the instrument is not operated within 5 minutes, the instrument will enter the off-screen state; if the instrument is not operated within 1 minute after the screen is off, the instrument will automatically shut down.

(2) Calibration
Automatic calibration description: The instrument has the function of automatic calibration at startup, but in order to use the instrument more conveniently and flexibly, it is designed to choose whether to automatically calibrate at startup. That is, when the last shutdown was manual shutdown, the next startup will automatically calibrate;

When the last shutdown is 5 minutes after the screen is off, it will automatically shut down, and it will not automatically calibrate the next time it is turned on. When the environment in which the instrument is used changes (such as drastic changes in temperature, altitude, humidity, etc.), the instrument must be calibrated. To ensure accurate calibration, please use the standard plate provided by the original factory. The dust on the standard board will affect the calibration effect. Before calibration, please wipe the working surface of the standard board with a cloth to make sure the working surface is clean.

The standard plate is a precision optical component, so avoid exposure to light and keep it properly. Due to environmental factors, the photometric data of the standard plate will change over time. Therefore, we recommend that you regularly send the standard plate back to the original factory or a qualified metrology institute for calibration testing (recommended once a year).

(3) Measurement
The gloss meter is automatically calibrated when it is turned on, and the operation method is simple and convenient. The measurement mode is the basic mode. The basic mode is the sample measurement mode, which directly displays the gloss measurement value, which belongs to a single measurement, and can display 3 sets of measurement data at the same time.

Matters needing attention in gloss meter test:
1. The calibration plate of the gloss meter must be kept clean without dust and stains. If the standard plate is not clean, the entire test data will be incorrect. Correct operation should be placed directly on the base of the gloss meter.

2. The gloss meter must have a self-test and self-calibration function when it is turned on, automatic diagnosis, and timely detection of problems caused by system errors, improper operation, and contamination of the standard plate that the instrument cannot pass the self-calibration.

3. After the gloss meter is used up, the storage environment should avoid heat sources and corrosion, and store it in a dry place.

Gloss meters AGM-580 are mainly used in the surface gloss measurement for paint, plastic, metal, ceramics, building materials. It conforms to the DIN67530, ISO2813, ASTM D523, JIS Z8741, BS 3900 Part D5, JJG696 standards and so on.

AGM-580_Gloss Meter with 3 Angles (20, 60 and 85º)